Combination high tension switch fuse



April 10, 1934. T. E. MURRAY, JR

COMBINATION HIGH TENSION SWITCH FUSE Original Filed Feb. 29, 1928 3 Sheets-Sheet l hum April 10, 1934. r. E. MURRAY, JR

COMBINATION HIGH TENSION SWITCH FUSE Original Filed Feb. 29. 1928 3 Sheets-Sheet 2 I M A TTORVE V April 10, 1934. T. E. MURRAY, JR

COMBINATION HIGH TENSION SWITCH FUSE 3 Sheets-Sheetv Original Filed Feb. 29, 1928 Patented Apr. 10, 1934 UNITED STATES CODIBINATION HIGH TENSION SWITCH FUSE Thomas E. Murray, Jr., Brooklyn, N. Y., assignor to Metropolitan Device Corporation, a corporation of New York Application February 29, 1928, Serial No. 257,861 Renewed September 12, 1933 8 Claims.

The invention aims to provide an improved and simplified means for disconnecting the parts of a high voltage circuit. On such lines it is common to employ elaborate and expensive circuit breakers usually operating in oil, to avoid arcing-over between the parts of a switch and burning or pitting of the switch contacts. By the present invention these complications and expenses can be largely obviated.

The accompanying drawings illustrate embodiments of the invention.

Fig. 1 is a side elevation partly in section of the invention applied to a knife switch.

Fig. 2 is a perspective view of the same.

Figs. 3 and 4 are respectively a side elevation and a front elevation of a modification.

Fig. 5 shows one of the fuses in section.

Referring to Fig. 1, the incoming bus bar 1 of the circuit is mounted on the barrier or other support 2. On the opposite side of the barrier is a switch blade 3 pivoted on a support 4 which is connected through the barrier to the bus 1. The switch blade may be actuated by means of an arm 5 connected by an insulated link 6 with the core 7 of a quick-acting solenoid 8.

The out-going bus 9 also mounted on the rear of the barrier carries fixed blade 10 in line with the opening 11 in the barrier registering with the lateral projection 12 on the switch blade. Normally the projection 12 engages the contact 10 and the normal current flows from one to the other bus bar through the switch blade in the manner indicated by the full line arrows.

The switch blade 3 has an extension 13 carrying a set of end contacts 14, 15 and 16 adapted to engage respectively the contacts 17, 18 and 19. These are separate contacts each of which is separately mounted on a bracket 20 supported from an insulating bracket 21. Between the bus bar 9 and the several brackets 20 there are inserted a number of fuses corresponding to the number of switch blades 17, 18 and 19 (which may be any desired number) The fuses are preferably of a type covered in certain prior applications of Thomas E. Murray; for example Ser. No. 252,439 filed Feb. 7th, 1928.

Fig. 5 shows one of the fuses in section. An open ended tubular case 22 carries a pair of plungers 23 of insulating material adapted to slide freely in the case. The fuse strip 24 has a blowing point 25 located between the plungers at points adjacent thereto. The fuse strip is imbedded and fastened in the plungers. The gas generated by the blowing of the fuse is, therefore, confined and the plungers with their engaged portions of the fuse strip are blown quickly away from the blowing point and out of the open ends of the casing or to such a distance that the circuit cannot be reestablished by the passage of the current through the gas generated. The material and dimensions of the fuse strip and the spacing between the plungers are so calculated that the portion of the strip between the plungers will, on gasification, be suificient to give the desired quick and wide separation of the plungers with their ends of the fuse strip. The amount of the fusible metal which will be fused or gasified when the blow-out occurs is determined by the spacing between the plungers, and is limited by the plungers. The plungers embed the fuse strip so closely that the arc cannot penetrate to a substantial extent, so that the spacing of the plungers determines the quantity of metal which will be gasified.

The leads 26 and 27 to and from the fuse strip are located on opposite sides of a horizontal barrier 28 projecting outward from the back of the main barrier 2. By this arrangement we have a repulsion effect between the two conductors 26 and 27 on the opposite sides of the insulating barrier, which also tends to throw the ends of the fuse strip apart when the reduced portion thereof burns through. The single barrier 28 (Fig. 2) is used for the entire group of fuses, the casings of the latter being fixed in the outer end of the barrier.

Now when it is desired to break the circuit under a load between the busses 1 and 9 the switch blade 3 is swung outward. When the contact 12 leaves the contact 10, the main connection between the two busses is broken. But there is still a path for the current as indicated by the dotted line arrows through the extension 13 of the switch blade and the contacts 14 and 17 and through the fuse to the out-going bus 9. Fig. 1 shows this, which is an intermediate position of the parts. The out-going movement of the switch blade will be continued beyond the position shown. But when this position occurs the flow of the full current through the fuse blows the latter and completely breaks the circuit between the busses. The further movement of the switch blade carries the contact 14 clear of contact 17;

Two or more of the fuses may be connected by swinging down the opposite contacts 17, 18

and 19 shown in Fig. 2. But ordinarily one fuse in the circuit will serve the desired purpose. Assuming one fuse to be used, then when the switch blade 3 is restored to its connecting position the fuse which has just blown will of course be useless and another fuse is introduced into the circuit by lowering one or more of the pivoted contacts 18 and 19.

In order not to blow the fuse on the closing of the switch, under a load, the main switch is first closed and then later on one of the small auxiliary switches, No. 17, 18 or 19 is closed. (See Fig. 2).

The fuse thus serves as a protection for an instant during which the switch is open. The current having a path through the fuse at this instant there is no arcing across the main switch contacts and no burning or pitting of the latter.

The fuse is located entirely behind the main barrier. It may be outside of the wall of a building for example. The certainty of a wide and sudden separation of the ends of the fuse strip insures against danger of reestablishing the current through this part of the installation. The horizontal barrier 28 prevents the upper part of the fuse strip and conductor from engaging the lower parts. An ordinary comparatively cheaply made switch may be used in installations where now elaborate and extremely expensive oil circuit breakers are thought necessary. On such installations the switches are not opened very frequently, and the cost of the fuse destroyed is trifling. The improvement may be applied also to other types of switch, including oil circuit breakers. Various other means may be provided for replacing fuses; such for example as a common automatic fuse-replacement mechanism.

With an installation of the type illustrated I have used 10 ampere fuses successfully in opening switches on which there were loads of 200 amperes at 2500 volts and loads of 100 amperes at 6600 volts.

The parts must be so arranged that the switch blade will reach its full open position, or such a position that there can be no danger of arcing, before the circuit through the fuse is entirely broken. Otherwise there is danger of the current re-establishing itself across the main switch contacts. A quick-opening switch should therefore be used, particularly where we have a small quick-opening fuse. It will be understood that other types of fuse may be used and that, whatever type be used, they may be proportioned to break at greater or less speed. The solenoid 8 shown in Fig. 1 exerts a quick and powerful pull on the arm 5, and the movement is multiplied "at the switch contact 12 by reason of the increased length of its lever arm, so as to provide a quick and wide opening movement of the switch blade. Various other operating means may be used. In Fig. 2, I have shown a handle 29 on the lower end of the switch blade. This however is merely typical of various manual or power operating devices.

The circuits and connections may also be arranged in various ways to pass the current through the fuse while the main switch contacts are being separated.

In the arrangement of Fig. 3 the in-coming wire is carried in a socket 30 connected to a bracket 31 on which is provided a switch blade 32, the free end of which engages contacts on the bracket 33 carrying the socket 34 for connection to the out-going conductor. The brackets 31 and 33 are mounted on the face of the barrier 35. On the back of this barrier is a fuse case 22' carrying plungers and a fuse strip 24 the same as in Fig. 5,'the ends of the fuse strip or conductors leading therefrombeingconnected by binding screws to conducting terminals 36 and 37 which pass through the barrier to make connection with the respective brackets or switch terminals 31 and 33.

The operation is the same as for the arrangement of Fig. 1. When the switch blade leaves the contacts on the bracket 33 there is an instant during which the current flows through the fuse; thus saving injury to the switch contacts and avoiding the danger of arcing across the switch. In this case as in the case of Fig. l, the fuse is always carrying a small portion of the current. The parts may be so arranged however that in the closed portion of the switch the fuse will be out of circuit and that it will be brought into the circuit only during the opening of the main switch and before the contacts of the latter are separated.

It will be understood that the fuse illustrated is not the usual fuse of comparatively large capacity designed to blow when an overload occurs on the circuit. The circuit will usually be provided with such overload fuses in addition to the fuse of this invention for deliberately opening the circuit when desired.

Such a combination, however, is not claimed in the present application, being covered in a copending application of Thomas E. Murray, No. 296,881, filed August 2, 1928.

Various other modifications may be made by those skilled in the art without departing from the invention as defined in the following claims.

What I claim is:

1. An electric circuit comprising a barrier, a pair of terminals, a switch blade on one side of said barrier, said switch blade being permanently connected to one terminal and having a breakable connection to the second terminal, a fuse connected to said second terminal and a contact connected to said fuse and contacting with said switch blade, said switch blade being separable from said contact after its separation from said second terminal.

2. An electric circuit comprising a barrier, a pair of terminals, a switch blade pivoted to one terminal on one side of said barrier to contact with a second terminal, a third terminal contacted by said switch blade and a fuse on the opposite int side of said barrier connected between said sec- 0nd and third terminals, said third terminal having contact with said switch blade after its separation from said second terminal.

3. An electric circuit comprising a barrier, a terminal mounted on said barrier, a switch blade pivoted to said terminal on one side of said barrier, a second terminal and a third terminal positioned'to be contacted by said switch blade and a fuse having an expellable plug and a fuse wire extended therethrough at the opposite side of said barrier from said switch blade and connected between said second and third terminals.

4. An electric circuit comprising a barrier, a terminal, a switch blade pivoted to said terminal at one side of said barrier, a second terminal posi- 5. An electric circuit comprising a terminal,

a switch blade pivoted to said'terminal, a second terminal positioned to be contacted by said switch blade in closed position, a series of fuses, a series of spaced terminals, means connecting said fuses in parallel between said second terminal and said series of terminals, and means individually to contact said switch blades with said fuse terminals in a partly open position of said switch blade.

6. An electric circuit comprising a terminal, a switch blade pivoted to said terminal, a second terminal and a third terminal positioned to be contacted by said switch blade, and a fuse having an expellable plug, and a fuse wire extended therethrough connected between said second and third terminals.

7. An electric circuit comprising a pair of terminals, a switch blade pivoted to one terminal to contact with a second terminal, a third terminal contacted by said switch blade, and a fuse connected between said second and third terminals, said third terminal having contact with said switch blade after its separation from said second terminal.

8. An electric circuit comprising a pair of terminals, a switch blade permanently connected to one terminal and having a breakable connection to the second terminal, a fuse connected to said second terminal, and a contact connected to said fuse and contacting with said switch blade, said switch blade being separable from said contact after its separation from said second terminal.

THOMAS E. MURRAY, JR. 

